There are several commercial methods for preparing the rotor housing of a typical rotary internal combustion engine. One popular method entails preparation of a core surface which is the mirror image of the intended inner wall of the rotor housing. The core electroplated with a thin coating of chromium over which is flame sprayed powdered plain carbon steel to form a relatively thick porous self-fused coating on the core. The selection of spray coated materials is limited due to the particular technique involved; the material must attempt to provide adherency to the surrounding housing. The spray coating and core are carried as an assembly to a die-casting machine where a mass of aluminum is cast thereabout to form an integral composite. The core then is stripped from the chromium coated liner to leave in tact the composite rotor housing. The principal drawbacks of this transplant technique are: (a) plain carbon steel, not being sufficiently wear-resistant by itself performs only as a metallurgical intermediate for bonding with aluminum, and the chromium coating, serving as the wear-resistant portion, experiences undesirable heat checking; (b) the considerable porosity of the sprayed powdered liner reduces heat transfer through the housing lowering the efficiency of the cooling system. The chromium coating, in addition, is extremely thin and can be easily damaged during assembly and fabrication. The high expense of the multiple steps involved is undesirable.
Turning to another body of technology, the prior art recognizes that a particularly useful material for wear-resistance is that of an electrolytic deposit of a nickel base with suspended particles of silicon carbide. Such deposit has been known for some time and has been used for various products including rotor housings for rotary engines. However, such deposit has been invariably applied by a direct electrolytic method that is directly on the housing itself or other end product.
The prior art has not appreciated how to prepare a transplant liner by electrolytic techniques which will effectively bond to a casting thereabout. Nor has the prior art appreciated how to utilize and electrolytically deposit such wear-resistant materials as nickel-silicon carbide in functional thicknesses greater than 0.02 inches which will not deteriorate under a severe heat stress environment. Nor has the prior art appreciated how to impart a superior smooth as-deposited surface to a rotor housing to obviate substantial machining.